The U.S. Federal Aviation Administration's drone registration system is about to hit the 400,000 mark, three months after it was launched.

"That’s really quite remarkable, and we are very encouraged by these numbers," said FAA Administrator Michael Huerta, speaking at the South by Southwest conference in Austin, Texas, on Monday.

The FAA developed the registration system with input from the drone industry. It's less about the FAA tracking drone pilots than about educating them on drone safety.

With thousands of new drones in the sky, the FAA is eager to remind pilots that they are using shared airspace and need to remember certain rules of the sky.

The rules prohibit flying drones above 400 feet, out of sight, at night, close to airports, or over people. The registration process, which can be done online and takes a few minutes, asks pilots to acknowledge these rules.

"It is a way of letting operators know that as soon as they start flying outdoors, they are, in effect, pilots," said Huerta.

The FAA has been under pressure to allow more routine commercial use of drones. Companies need to apply for specific permission, but the agency is considering new rules that would relax that restriction. Companies like Google, Amazon and Walmart are keen to use drones for package delivery, but other companies want to routinely use drones for things like photography, surveying and surveillance.

On Monday, the FAA also launched an Android version of its B4UFLY app, which provides pilots with a quick overview of local flight restrictions that govern drone flight.

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